No, it is a mater of more friction and less lubrication. Because the piston expands more at the exhaust side because it is much hotter over there the piston will create an egg shape pushing against the sleeve. Because there is no transfer port there is also less lubrication. With both things hapening it can create scratches and the amount and how deep is depending how carefull you are heating up the engine.

This is brand new engine with dirty manifold and pipe.

It happened twice with the same manifold and pipe ( 3 years I never clean the inside, ie. dirty )

The engine quit working after just few laps. I check the engine exhaust port and notice big scratches on the exhaust port.

I suspect the turbo charge effect ( or sonic pulse created from the pipe's cone ) is pulsing back some carbon dirts from manifold into combustion chamber.

Roelof, I'm not engine expert though ......

I'm open to your ideas or anyone ideas.

My mechanic said the main bearing is not good ..... however this is brand new engine.

No problem whatsoever during break in process.

It happened on its first day of racing ( heat 1, dnf, 5 laps and done ).

that's most likely not due to a dirty pipe-I had the same thing happen on a newly broken in engine and new pipe set (JPGIMAR Mig 21 R09 prerun). Piston got stuck at the top of the sleeve and shut the engine down during a race. Open it up had very similar scratches on the exhaust side.- I'm still running this motor without fault several gallons later- I was told the same thing; to properly warm the engine before racing as well as avoiding certain fuel brands

That I have seen more and was related to the last batch "microcasted" pistons and since that they have switched to the CNC piston in combination with small lubrication ports just under the exhaust port and later on to coated pistons. Novarossi knows what did go wrong but do not tell....

We have discussed about this issue and someone mentioned it could be a cold weld due the tigth fit. Normally an engine will stop/lock itself when the engine is not fuly runned in and you want to go to fast during the warm up. With this piston it seems it locks itself and directly has broken loose to run on. I could be a lack of lubrication with a different material piston.

In my previous post I was talking about tiny visable scratches not a compleetle damage surface....

I concur with Roelof. I've had several painful and expensive experiences where my very new pistons looked just like the ones you've posted.

Causes : Not enough lubrication + mixture too lean.

Exhaust port section of the piston heat expands more and couple with a lack of oil, jams itself against the port opening on the liner. It has nothing to do with a 'dirty' manifold or pipe.

Since my experience, I stopped using fuel with less than 11% oil and more specifically full synthetic lubrication fuel. Castor oil gives better high temp and RPM lubrication. A good mix of synthetic and castor oil is imperative for these ultra high revolution on-road engines until technology gives us better synthetic oil for our micro engines.

Also, once I feel my engine is peaking, I back off the HSN a little s that I can be sure my engine is if anything slightly on the 'rich' side.

Those scratches are not caused by foreign debris. Looks like seized piston probably due to a combination of tight engine and high RPM's while engine was cold and sleeve had not expanded.

[QUOTE=asw7576;11042560]This is brand new engine with dirty manifold and pipe.

It happened twice with the same manifold and pipe ( 3 years I never clean the inside, ie. dirty )

The engine quit working after just few laps. I check the engine exhaust port and notice big scratches on the exhaust port.

I suspect the turbo charge effect ( or sonic pulse created from the pipe's cone ) is pulsing back some carbon dirts from manifold into combustion chamber.

Pls ignore. PM sent to Roelof.

What is the difference between c8tgf and a c8tgh . I road race a plus 28 7 port. The c8tgh workes fine but the c8tgf is less expensive .

Any advice ?
Cheers Greg T

What is the difference between c8tgf and a c8tgh . I road race a plus 28 7 port. The c8tgh workes fine but the c8tgf is less expensive .

Any advice ?
Cheers Greg T

do anybody can tell what is the difference between 35 plus 21 and 35 plus 21A
performance and runtime?

thks in advance

http://www.amainhobbies.com/product_...ine-Turbo-Plug

The c8tgf is slightly colder than the c8tgh.

The A means front, and rear steel bearings. Normally the 35+21 comes with a ceramic rear bearing, steel front.

The A version is a good option if your on a budget, but the ceramic rear bearing will add performance, and runtime. Although slightly.

thks for the info